TITLE: Paying Attention to the Details AUTHOR: Eugene Wallingford DATE: September 16, 2004 4:01 PM DESC: risk is a combination of factors -- attend to those, too ----- BODY: At PLoP last week Gerard Meszaros said something that caught my ear:
risk = probability X consequence Why waste energy minimizing a risk whose consequence is too low to be worth the effort?
This idea came up later at the conference when Ward talked about the convention-busting assumption of wiki, but it is of course a central tenet in the agile methods. Too often, when faced with an undesirable potential result, we focus too quickly on the event's likelihood, or on its effects. But risk arises in the interplay between the two, not in either factor alone. If an event is likely to happen but has only a small negative effect, or if it has a major effect but is unlikely to occur, then our risk is mitigated by the second factor. Recognizing this can help us avoid the pitfall of running from a potential event for the wrong reasons. Recognizing this relationship can also help us to take control of the problem. In XP and the other agile methods, we accept that change is highly likely, so we work to minimize the consequence of change. We do that by maintaining a comprehensive suite of tests to help us verify that changes to the system don't break something unexpectedly; and, when they do, we use the tests to find and fix the problem spots. We minimize the consequence of change by using refactoring tools that help us to change the structure of our programs when design requirements call for something different. We minimize the consequence of change by working on short iterations, continuously integrating our code, and releasing versions frequently, because these disciplines ensure that we get feedback from our tools and client frequently. Learning to pay attention to all the variables in a situation is more general than just assessing risk. In a recent message to the XP mailing list, Kent Beck said that he tries to help his customers to think in terms of return, not just value or cost:
I have another goal for early estimation, which is to encourage the business-decision-makers to focus on return instead of just value. If the choice is between the Yugo and the Ferrari, I'll take the Ferrari every time. If I have $6000 and I know the price of the two cars, my thinking is more realistic.
A system's value is a function of many variables, including its features, its cost, and the environment in which it must operate. We can become more accurate, more efficient decision makers by paying attention to what really matters, and not being distracted by our biases and initial reactions. Often, these biases were learned in other times, other environments. Fortunately, I think that this is something that we can learn to do, by consciously developing new habits of thought. It takes discipline and patience to form new habits, but the payoff is often worth the effort. -----